The trail to the Chimneys is one of the easiest in Big Bend. Granted, it may
be a wee hot in the summer (we did it in June), and you have to watch for the
horse-crippler cactus
(Echinocactus texensis - I got one through the sole of my shoe), but the
trail is well-developed and
the topography almost level. A stroll of only three miles gets you there.

You see, in the image below, the trailhead with Kit Mountain to the left,
shadowed by clouds, and Black Mesa in the distance, mostly in sunlight. The
view is almost due west. Black Mesa gets its name from the dark Alamo Creek
Basalt, which was erupted
between 47 and 34.5 million years ago and forms the top of the mesa. In moist
places like Hawaii, basalt quickly weathers to red soil, but it tends to be
more resistant in dry areas such as Big Bend. In addition, not all of the Alamo
Creek Basalt is actually basalt. It consists of several lava flows, some of
which are
trachyandesite in
composition, which is a
volcanic
rock with more
silica and
alkali metals than
basalt. The Alamo Creek basalt flows themselves are also alkaline. The Alamo
Creek basalt extends from here north to Dogie Mountain (just outside the west
side of the park) and west to the town of Lajitas (just outside the southwest
side of the park along the Rio Grande). (The most interesting thing about
Lajitas is that its mayor is a beer-drinking goat named Clay Henry, party
affiliation unclear.)

In the picture below, my brother, Randy, is snapping a telephoto just
as a swath of sunlight illuminates the chimneys. His photo is displayed in the
next picture. (The first photo was also taken with magnification, but not as
much as Randy's.) The clouds were certainly welcome due to the heat,
even though they did make photography difficult. The Chimneys are about 2.5
miles away at this point, and Black Mesa is several miles beyond that. Note
how green the vegetation is. This was in 2007 after an unusually wet spring in
West Texas.

.

The next three images are of the Chimneys. The gap in Mesa de Anguila
(Sierra Ponce in Mexico) marks the eastern margin of Santa Elena Canyon.
The Big Bend website says the Chimneys are a
volcanic dike,
whereas the book Big Bend Vistas by William MacLeod claims they are a
row of volcanic necks
This latter interpretation seems unlikely to me. On the the other hand neither
interpretation explains the stratification that seems to be present in these
outcrops. However, if this apparent
stratification is due to weathering as ground level was lowered by erosion,
then I would favor the volcanic dike interpretation.

The premier attraction of the Chimneys is the display of Native American
petroglyphs. The image below shows the pillar of rock on which petroglyphs
were inscribed.

The picture below is a close-up of the petroglyphs. I'm sure archeologists
would find meaning in these, but how do they know they weren't made by
Native Americans bored out of their skulls? After all, what can you do in the
desert for fun? Well, if you have a gun, target practice using the petroglyphs
might be one possibility. Note the circular petroglyph toward the upper right,
riddled with bullet marks. One can imagine drunken cowboys, also bored
out of their skulls, taking potshots at it. Now, whether or not this is
desecration, depends on when it was done. If it was done long enough in the
past, it would now be history. On the other hand, inscribing your initials in
the fireplace of the historic Homer Wilson Ranch, as we witnessed on a
backpacking trip along the Dodson Trail, is definitely desecration.

To the south of the Chimneys is Bee Mountain with layers of Chisos Group
volcanics showing as outcrops. Also note Santa Elena Canyon to the right. (The
Chisos Group of rocks consists of 47 to 32 million year old sediments,
tuffs, and lava flows.)

The following view is looking west from the Chimneys. In the
distance are the high Chisos Mountains, Carosel Mountain, and Elephant Tusk (an
igneous intrusion). Between
Carosel Mountain and the high Chisos lie the Sierra Quemada (Burned Mountains).
Carosel Mountain overlooks the ranch house of pioneer rancher, Homer Wilson.

Your constant companion on the Chimneys trail is the east-west elongated
Kit Mountain on your south, and it is time to take a look at this feature. In
the image below you can see the bulk of the mountain consists of Chisos
volcanics (note the white volanic tuff) with a cap of Burro Mesa
Rhyolite. Rhyolite is a
volcanic rock high in silica, and tuff is
hardened volcanic ash produced by an explosive volcanic eruption.

On the west end of the mountain is a bit of an unusual feature, or at least
so it seems to me. Behind the ridge in the foreground is a depression that
apparently forms a dry lake bed. This depression may be due to the fault that
has been mapped to run along the northern border of the mountain.

As you approach the trail head on your way back, you get a great view of
the layer-cake
stratigraphy of Goat Mountain (below). You can clearly see the volcanic
strata that have been unveiled by differential erosion. The dark strata at
the bottom of the mountain belong to the Bee Mountain Basalt. Above that are
Chisos volcanics, including the Mule Ear Spring Tuff (light color) and Tule
Mountain Trachyandesite. At the top are the two members of the Burro Mesa
Formation: the Wasp Spring Tuff and the Burro Mesa Rhyolite. Both were
erupted about 29 million years ago. The units below them were emplaced between
34 and 32 million years ago. (Note: Recent research has cast doubt on the
identification of the Tule Mountain Trachyandesite. This trachyandesite may have
been erupted three million years later than that identified as the Tule
Mountain unit.)

The oldest rock along the trail is the Ash Spring Basalt at 34.5 million
years. The next image is an outcrop of this rock to the north of the trail as
you approach the trail head and the end of your six-mile stroll.